基于双滑面模型的混凝土重力坝深层抗滑动力稳定分析方法

地震作用下混凝土重力坝的深层抗滑稳定是设计关心的问题。应用刚体极限平衡方法,并与有限元相结合进行重力坝深层抗滑稳定动力分析,制定了相关的计算流程:①通过黏弹性地基模型考虑地基岩体的辐射阻尼效应;②通过不同岩体中地震波速的分段处理确定入射波在不同岩体中的传播时间,从而考虑岩层的不均匀性;③应用直接计算截面内力的方法提取有限元结果中的滑动力和阻滑力,并采用规范给出的抗滑模型进行深层抗滑稳定分析;④通过敏感性分析确定了双滑面模型的2个关键参数,并比较了地基均匀性对结构变形和稳定的影响。基于上述计算流程,结合小南海重力坝工程实例,计算了地震作用下重力坝深层抗滑稳定安全系数,计算结果验证了方法的有效性,并与常规方法作了对比,其一致性较好。

A Method of Analyzing Deep Anti-sliding Dynamic Stability of Concrete Gravity Dam Based on Double Sliding Surfaces

The deep anti-sliding stability of concrete gravity dam under seismic action is an issue receiving much concerns in hydro-structure design. In this paper, an analysis method for the deep anti-sliding dynamic stability based on rigid body limit equilibrium method and finite element method is proposed and corresponding numerical process is formulated. Firstly, the radiation damping effect is considered by setting a viscous-spring artificial boundary condition in the foundation model; the seismic wave velocity and the arrival time of incident wave are set different by partitions to reflect the non-uniformity of rock strata. Furthermore, the factor of safety is calculated by decomposing external load into sliding force and drag force in the rigid finite element result by directly calculating the internal force of cross-section in the model with double sliding surfaces recommended in specification. Subsequently, the two key parameters of the model with double sliding surfaces are determined through sensitivity analysis, and the effects of foundation’s uniformity on deformation and stability of the structure are compared. The proposed method is verified to be effective by a calculation case study of Xiaonanhai gravity dam.